Field of the Invention
The invention relates to a valve plate made of fiber-reinforced plastic for gas exchange valves of reciprocating piston compressors which includes at least two concentric seal rings that cooperate with corresponding seating surfaces at the valve seat by way of profiled sealing surfaces and are connected through radial webs, wherein between the seal rings the webs are designed to be thinner over the entire radial extent thereof in comparison to the adjacent thickness of the seal rings and on both sides of the valve plate.
The Prior Art
Inlet and outlet valves for reciprocating piston compressors with high stroke volumes are currently usually plate valves with a large number of concentrically arranged flow openings that are either covered by a one-piece steel or plastic valve plate or cooperate with individually profiled rings. Although as a consequence of the necessarily mutual movement of all areas of the plate the one-piece valve plates enable a relatively even load on the sealing and stopping surfaces, which are put under considerable stress during opening and closing, they also have the disadvantage with regard to flow redirection and associated flow losses as a result of the cooperating sealing surfaces, which must be achieved. On the other hand, valves with individual seal rings can be designed relatively easily with sealing surfaces that are oblique in the flow direction (as so-called profiled rings), which results in less flow redirection and thereby less flow losses.
In order to achieve maximum efficiency at minimal strokes, such plate valves must be as delicately designed as possible and thereby with as many seal rings as possible in the case of individual rings. However, the probability of unpredictable and chaotic valve motions increases with the number of rings. This problem increases in highly lubricated compressors due to oil adhesion at the valve seat.
Profiled plate valves with valve plates of the type mentioned above represent a type of hybrid with the advantages of one-piece, un-profiled valve plates (common motion), and the advantages of individually profiled sealing rings (efficiency, robustness). However, this concept also has a serious disadvantage. Based on unavoidable minimal dimensional deviations during manufacture and different thermal expansion behavior, in seal rings with oblique seating surfaces there is necessarily always small gaps that do not close until the closing pressure is applied and the ring deforms. This sealing behavior depends primarily on the inversion/eversion stiffness of the ring, and also on the magnitude of the deviation of the cooperating sealing surfaces. However, in profiled valve plates of the type mentioned the connecting radial webs prevent individual deformation of the individual rings, wherein the adjacent rings, with individual deviations thereof, can have even more of an effect. Profiled, one-piece valve plates made of plastic are used only seldom for this reason, and only for special applications.
WO 0151811 A1 dated Jul. 19, 2001 discloses a valve plate for gas exchange valves that can be manufactured from fiber-reinforced plastic, comprising two concentric sealing rings that cooperate with corresponding seating surfaces at the valve seat by way of profiled sealing surfaces and that are connected by way of radial webs, wherein the webs can be designed to be thinned between the sealing rings on both sides of the valve plate in comparison to the thickness of the adjacent sealing rings.
DE 202609 C dated Mar. 17, 1907 discloses a valve plate with two concentric sealing rings connected together by way of radial webs.
DE 692442 C, dated Jun. 19, 1940 discloses a plate valve comprising a valve plate that has concentric sealing rings, wherein cylindrical wound springs sit against the flat back side of the valve plate.
EP 0572748 A1 discloses a ring valve with a valve plate that comprises concentric sealing rings, wherein centering and if necessary holding knobs or depressions are provided at the back side of the valve plate for the valve springs.
The object of the present invention is to improve upon valve plates of the type mentioned above such that the sealing behavior at least approximates that of concentric individual rings using simple means, the advantages of one-piece valve plates still being retained with regard to the common movement of all sealing rings nevertheless.